Ecg electrode and leadwire connection integrity detection

ABSTRACT

A system and method for ECG electrode and leadwire connection integrity detection are provided herein. The system includes a plurality of electrodes wherein a uniform spectral energy signal is to be injected into a subset of electrodes of the plurality of electrodes. The system also includes a computing device. The computing device includes a display, and the computing device is communicably coupled to the plurality of electrodes. The computing device is configured to acquire input signals from an electrode and determine a frequency response from the electrode based on the input signal from the electrode. The computing device is also configured to determine impairments in the electrode and leadwire connection using the frequency response.

BACKGROUND

An electrocardiograph is a device adapted to record the electricalactivity of a patient's heart over time. The electrocardiograph includesone or more sensors or electrodes adapted for attachment to a patientand configured to sense electrical activity. The electrodes transmitelectrical signals pertaining to the cardiac activity via a conductorsuch as a wire to a controller. The controller may generate a plotreferred to as an electrocardiogram (ECG) based on the data from theelectrodes.

In conventional ECG acquisition, one electrode is driven to a directcurrent (DC) potential such that the common-mode potential appearing atall of the other electrodes falls within the common-mode signal range ofthe ECG input amplifiers. The electrode may also be driven with a simpleout-of-band tone in order to detect major lead failure conditions, suchas an open circuit. However, this conventional ECG acquisition does notprovide any additional information regarding the failure condition.

BRIEF DESCRIPTION

An embodiment relates to a system for ECG electrode and leadwireconnection integrity. The system includes a plurality of electrodeswherein a signal with uniform spectral energy is to be injected into asubset of electrodes of the plurality of electrodes. The system alsoincludes a computing device. The computing device includes a display,and the computing device is communicably coupled to the plurality ofelectrodes. The computing device is configured to acquire input signalsfrom an electrode and determine a frequency response from the electrodebased on the input signal from the electrode. The computing device isalso configured to determine impairments in the electrode and leadwireconnection using the frequency response.

Another embodiment relates to an ECG system. The ECG system includes aplurality of electrodes including a right leg electrode and a secondelectrode. The right leg electrode is to be driven by a chirp signal andto be releasably attached to a patient. An impedance between the secondelectrode and the right leg electrode is calculated, and the calculatedimpedance is used to determine a location of electrode connectionimpairment.

Still another embodiment relates to a method for ECG electrode andleadwire connection integrity detection. The method includes injecting achirp signal into a neutral electrode, and measuring an impedance at aplurality of electrodes across a range of frequencies from the chirpsignal. The method also includes calculating an impedance of pairs ofelectrodes of the plurality of electrodes from the measured impedance,and determining an impairment location based on the calculatedimpedance.

BRIEF DESCRIPTION OF THE DRAWINGS

The present techniques will become more fully understood from thefollowing detailed description, taken in conjunction with theaccompanying drawings, wherein like reference numerals refer to likeparts, in which:

FIG. 1 is an exemplary illustration of a 12-lead ECG system inaccordance with embodiments;

FIG. 2A is an illustration of a right arm reference electrode withcommon-mode feedback and chirp signal driving the right leg electrode,in accordance with embodiments;

FIG. 2B is an illustration of electrodes and chirp signal driving leftarm, right arm, and chest electrodes in accordance with embodiments;

FIG. 3 is an example of a chirp signal according to embodiments;

FIG. 4 is a process flow diagram of a method for determining electrodeand leadwire connection integrity detection; and

FIG. 5 is a block diagram of a patient monitoring device used inaccordance with an embodiment.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which is shown byway of illustration specific embodiments that may be practiced. Theseembodiments are described in sufficient detail to enable those skilledin the art to practice the embodiments, and it is to be understood thatother embodiments may be utilized and that logical, mechanical,electrical and other changes may be made without departing from thescope of the embodiments. The following detailed description is,therefore, not to be taken as limiting the scope of the presenttechniques.

To obtain an ECG plot, a set of electrodes are releasably attached tothe body of a patient at various locations. The positioning of eachelectrode directly affects the quality and accuracy of the ECG. Theelectrodes are connected to electrode lead wires via an electrode head.The other end of the leadwires are connected to machinery that processesthese electrical signals and produces data characteristic of the bodyfunction being monitored. In embodiments discussed herein, an impedanceof the electrodes and lead wire connection to the patient is evaluatedover a range of frequencies. A technical effect of at least oneembodiment includes a chirp signal injected into an electrode. In somescenarios, the chirp signal has a uniform spectral energy contentsimilar to an impulse so that the impedance of the electrodes andleadwire connection can be evaluated over a range of frequencies. Inthis manner, a more comprehensive assessment of the patient electrodeand leadwire connection integrity is enabled in order to provideguidance to the caregiver on obtaining the best quality ECG recording.

FIG. 1 is an exemplary illustration of a 12-lead ECG system 100 inaccordance with embodiments. The 12-lead ECG system 100 provides twelveleads, pictures, or views of the heart through ten electrodesstrategically placed on a patient 102. Although a 12-lead ECG system isdescribed, the present techniques may be used with any number of leadsin any diagnostic/monitoring system.

The 12-lead ECG system 100 in the example of FIG. 1 enables twelve viewsof electrical activity of the heart of patient 102 via the tenstrategically placed electrodes. Four electrodes are limb electrodeswhich include a right arm (RA) electrode 104; a left arm (LA) electrode106, a right leg (RL) electrode 108; and a left leg (LL) 110. Althoughelectrodes RA 104 and LA 106 are shown as being attached to thepatient's 102 wrists, they are may be applied at the patient's 102shoulders. Similarly, although the electrodes RL 108 and LL 110 areshown as being attached to the patient's 102 ankles, they may be appliedto the patient's 102 hips. In some cases, the RL 108 is considered a“dummy” or neutral electrode that functions as a ground.

The remaining six electrodes are applied to the chest of the patient102. The six electrodes may be are placed at the 4th intercostal spaceright sternal edge (V1) 112, the 4th intercostal space left sternal edge(V2) 114, over the apex (5th ICS mid-clavicular line) (V4) 118, halfwaybetween V2 and V4 (V3) 116, at the same level as V4 but on the anterioraxillary line (V5) 120, and at the same level as V4 and V5 but on themid-axillary line (V6) 118. The 12-leads or views of electrical activitycan be acquired directly from the patient leads as well as derived usingEinthoven's law. The electrodes V1 112, V2 114, V3 116, V4 118, V5 120,and V6 122 must be placed with a high degree of precision on thespecific portions of the patient's 102 anatomy as illustrated in FIG. 1.

The process of attachment of the electrodes or leadwires to acquire ECGsignals is prone to conditions that can result in poor quality signals.The magnitude of the electrode/leadwire impedance has a significanteffect on the ability to obtain a quality ECG signal. According to thepresent techniques, the RL electrode is driven by a dynamic signal whichcan be controlled to output a low level chirp waveform imposed upon anaverage DC potential, thereby enabling a frequency response between eachof the electrodes to be determined by taking a Fast Fourier Transform(FFT) of the input signal appearing at each electrode. The frequencyresponse is then used to detect and classify impairments in theelectrode/leadwire connection of each ECG signal lead. In this manner,the location of the connection impairment can be accurately determined

The injection of the chirp signal results in improved feedback toclinician or patient in applying the electrodes, resulting in improvedacquisition of ECG signals, especially in a patient initiated recordinguse case. Further, an average right leg (RL) bias voltage can becontrolled in order to optimize the common-mode voltage appearing ateach of the ECG lead input amplifiers. In some cases, controlling theaverage RL common-mode voltage is used to account for variations inelectrode contact potential, reduce the chance of input amplifiersaturation, and improve the common-mode rejection performance of the ECGinput amplifiers.

In particular, the common-mode rejection performance can be improved byadjusting the chirp signal driving the RL so that it would center theinput signals from the electrodes within a range of the inputamplifiers, which would maximize the common-mode rejection and eliminateinput saturation of the amplifiers. Accordingly, the DC potential thatresults from attaching an electrode to a patient can be adjusted up ordown, eliminating the saturation in some cases and preserving the actualintegrity of the signals being measured.

FIG. 2A is an illustration of a right arm reference electrode withcommon-mode feedback and chirp signal driving the right leg electrode,in accordance with embodiments. As an example, chest electrodes V1 112through V6 122 are illustrated. The signal from each electrode is passedthrough an RL drive 202 with a sufficiently high corner frequency. Insome cases, the sufficiently high corner frequency is 40, 100, 150 Hz orhigher. The RA common-mode feedback to the RL drive 202 can remove apower line noise on the signal obtained from the plurality ofelectrodes. After the RLD 202, the filtered signals from electrodes V1112 through V6 122, LA 106, and RA 104 are sent through an amplifier204. The amplifier 204 may be a differential amplifier used to enhancethe difference between the electrode signals from the RA referenceelectrode.

The RL electrode 108 acts as an output and feeds signals back to thepatient. As illustrated, a chirp signal 206 is summed with the filteredand amplified output of the RA 104 electrode. The amplifier 204 of theRA 104 electrode has as inputs the filtered signal from the RA 104electrode and an amplifier bias 208. The summed chirp signal 208 and theamplifier bias 208 are input to an amplifier 210. The output of theamplifier 210 is filtered by a low pass filter 108 and then injected ordriven on to the RL 108 electrode. This dynamic RL bias drive circuitryenables the impedance from each of the leadwires and electrodes RA 104,LA 106, LL 110, V1 112, V2 114, V3 116, V4 118, V5 120, and V6 122 tothe RL 108 to be accurately measured over a predetermined frequencyrange. The measured impedance between the RL electrode and the otherelectrodes can then be used to calculate the impedance between any pairof electrodes or leadwires. This information can be used to notify theclinician or patient of which electrodes or leadwires require adjustmentor replacement before recording the ECG signals.

As illustrated in FIG. 2A, a high pass filter 212 filters the amplifiedsignals from the electrode V1 112 through V6 122, LL 110, and LA 106.Another amplifier 214 is applied to the electrode V1 112 through V6 122,LL 110, and LA 106. The amplifier 214 takes as input the respectivesignal from each electrode through the high pass filter 212 and theamplifier bias 208. The twice amplified signal is then sent throughanother low pass filter 216. After the low pass filter 216, eachelectrode V1 112 through V6 122, LL 110, and LA 106 can provide a leador view of the heart to be displayed on a monitor or printout.

Accordingly, the ECG electrode and leadwire connection integritydetection is enabled by spectral analysis of the injected chirp signal206. The chirp signal 206 has a uniform spectral energy content similarto an impulse so that the impedance of the electrode and leadwireconnections to the patient can be evaluated over a range of frequencies,versus measuring the impedance at a single frequency, as is commonlydone in current AC leadfail detection systems. By spreading the injectedenergy over a wide range of frequencies, a more accurate assessment ofthe patient interconnect impedance can be determined, including both theresistive and reactive (i.e., typically capacitive) components. Thisenables a more comprehensive assessment of the patient electrode andleadwire connection integrity in order to provide guidance to thecaregiver on obtaining the best quality ECG recording.

In embodiments, the chirp signal is a low level chirp waveform imposedupon an average DC potential, enabling the frequency response betweeneach of the electrodes to be determined by taking the Fast FourierTransform (FFT) of the input signal appearing at each electrode. Thefrequency response is then used to detect and classify impairments inthe electrode and leadwire connection of each ECG signal lead. Thisinformation can also be used to accurately determine the location of theconnection impairment.

In embodiments, the present techniques are able to determine a poorelectrode connection to a patient at low frequencies. A conventional ECGsystem can detect a good capacitive reactive impedance connection to thepatient via a 250 Hertz (Hz) signal used to evaluate the impedance andfrequency response of the electrodes at the single 250 Hz frequency.However, an electrode or leadwire connection to a patient can be a poorconnection at lower frequencies while showing a good connection at a 250Hz frequency. The present techniques can be used to detect the poorconnection at the lower frequencies. Additionally, the presenttechniques can be used to determine a low frequency impairment resultingfrom an impedance that is higher than a particular threshold at anelectrode or leadwire connection.

As illustrated in FIG. 2A, signals from each input electrode aremeasured with respect to the right arm, as the right arm signal servesas an input to an amplifier for the other electrodes. The amplifiers,such as the amplifiers 204, are to measure differential signals.However, there is a certain range of common mode voltages that theamplifiers can amplify. In accordance with the present techniques, theRL electrode 108 is used to apply a potential to the patient such thatall the other amplifier inputs are biased correctly and the voltagepresent at the other electrode inputs is valid for the amplifiers thatare actually attached to the patient at this point.

In some cases, a differential amplifier such as amplifier 204 canmeasure the difference between two voltages, and as long as the absoluteor common-mode voltage is within a certain range the amplifier 204 canamplify the signals. For example, if the amplifier has its powersupplied at −5 and +5 volts, it can amplify the different signals aslong as the input voltages on each of the differential inputs are withinthe −5V to +5V range. If the differential inputs are outside of thatrange, the amplifier will not work correctly as a linear component.Accordingly, applying a potential to the right leg of the patientbasically biases the amplifiers to ensure the differential inputs arewithin the correct range. Further, applying the chirp signal to theright leg gives a driven output that can generate more than a DC signal.The signals are biased and analyzed across a range of frequencies todetect a wider range of connection impairments when compared to aconventional ECG system.

FIG. 2B is an illustration of electrodes and chirp signal driving leftarm, right arm, and chest electrodes in accordance with embodiments. Asan example, chest electrodes V1 112 through V6 122 are illustrated. Thesignal from each electrode is passed through the RL drive 202 asdescribed with respect to FIG. 2A. After the RL drive 202, the filteredsignal is coupled with a chirp signal 206 that has passed through a leadcheck coupling 218. The signal then proceeds through an amplifier 204.The second input on the amplifier 204 is from the RA 104 electrode inorder to bias and amplify the filtered signals.

FIG. 2B illustrates an alternative technique of injecting the chirpsignal into each individual electrode input. The chirp signal isinjected as a current source (i.e., high source impedance) so that theamplitude of the chip signal picked up on each electrode input will be afunction of the impedance between that electrode and the RL electrodesuch that the higher the impedance, the large the chirp voltage will bethat appears on that particular input.

FIG. 3 is an example of a chirp signal 300 according to embodiments. Insome cases, the chirp signal 300 is a signal that has uniform spectralenergy content. As illustrated, the chirp signal includes valuesthroughout an entire frequency bandwidth (Hz) via a sinusoidal waveformof constant amplitude within particular time. In some embodiments, animpulse signal can be used instead of a chirp signal. Furthermore, otherwaveforms can be used by applying an inverse operation to arrive at auniform spectral density over frequencies applicable to ECG monitoring.

FIG. 4 is a process flow diagram of a method 400 for determiningelectrode and leadwire connection integrity detection. At block 402, achirp signal is injected into a subset of a plurality of electrodes. Insome embodiments, the subset is a neutral electrode, such as the RLelectrode as illustrated in FIGS. 2A. In other embodiments, the subsetof the plurality of electrodes include the chest electrodes, LLelectrode, LA electrode, and RA electrode as illustrated in FIG. 2B. Atblock 404, first impedance can measured at each electrode of theplurality of electrodes, and an impedance between pairs of electrodes iscalculated based on the measure impedances. At block 406, an impairmentlocation is determined based on the calculated impedances.

In some embodiments, the type of impairment can be classified dependingon the frequency response and calculated impedance at the electrode orleadwire connection. When the impedances or frequency responses areoutside of a pre-determined threshold, a connection impairment can bedetected and classified. In particular, an electrode or leadwirefailures at a lower frequency may indicate that the resistance of theconnection to the patient is too high. A high resistance at theconnection may be caused by a poor skin condition. In particular, thesurface of the skin where the electrodes are attached may need to beupgraded, or foreign substances may need to be removed from the skin,such as lotion or oils. Upgrading the skin can include, but is notlimited to, shaving hair or scrubbing the skin to enable a better skinto electrode connection.

A connection impairment can be detected prior to recording, displaying,or otherwise acquiring an ECG plot. In some cases, a connectionimpairment is included in a ECG preparation procedure. In someembodiments, the connection impairment may be determined duringacquisition of ECG signals. In this manner, the electrode connectionquality can be monitored throughout an ECG acquisition.

FIG. 5 is a block diagram of a patient monitoring device 500 that may beused in accordance with an embodiment. The patient monitoring device 500may be, for example, a electrocardiograph, a computing device, or anyother patient monitoring device that measures physiological parametersof a patient. The patient monitoring device 500 may include a centralprocessing unit (CPU) 502 that is configured to execute storedinstructions, as well as a memory device 504 that stores instructionsthat are executable by the CPU 502. The CPU may be coupled to the memorydevice 504 by a bus 506. Additionally, the CPU 502 can be a single coreprocessor, a multi-core processor, a computing cluster, or any number ofother configurations. Furthermore, the patient monitoring device 500 mayinclude more than one CPU 502. The memory device 504 can include randomaccess memory (RAM), read only memory (ROM), flash memory, or any othersuitable memory systems. For example, the memory device 504 may includedynamic random access memory (DRAM).

The CPU 502 may be linked through the bus 506 to a display interface 508configured to connect the patient monitoring device 500 to a displaydevice 510. The display device 510 may include a display screen that isa built-in component of the patient monitoring device 500. The displaydevice 510 may also include a computer monitor, television, orprojector, among others, that is externally connected to the patientmonitoring device 500. In some cases, the display is used to outputinformation on the status of a patient, including an ECG, connectionimpairments as described herein and various alerts.

The CPU 502 may also be connected through the bus 506 to an input/output(I/O) device interface 512 configured to connect the patient monitoringdevice 500 to one or more I/O devices 514. The I/O devices 514 mayinclude, for example, a keyboard and a pointing device, wherein thepointing device may include a touchpad or a touchscreen, among others.The I/O devices 514 may be built-in components of the patient monitoringdevice 500, or may be devices that are externally connected to thepatient monitoring device 500.

The computing device also includes a electrode hub 516. The electrodehub 516 may be coupled to a plurality of electrodes 518. In embodiments,the electrodes 518 form a 12-lead ECG system as described herein. Inother embodiments, the electrodes 518 form a 15-lead ECG system. Thepatient monitoring device 500 may also include a network interfacecontroller (NIC) 520 configured to connect the patient monitoring device500 through the bus 506 to a network 522. The network 522 may be a widearea network (WAN), local area network (LAN), or the Internet, amongothers. In some cases, the network 526 is a patient monitoring network.Additionally, in some cases, the network is secure. The patientmonitoring network can be used to measure and display physiologicalparameters, such as a patient's pulse rate and blood pressure.

The block diagram of FIG. 5 is not intended to indicate that the patientmonitoring device 500 is to include all of the components shown in FIG.5. Further, the patient monitoring device 500 may include any number ofadditional components not shown in FIG. 5, depending on the details ofthe specific implementation.

While embodiments are described herein with respect to cables used inthe medical field, the reference to patient monitoring systems may beinterpreted broadly. Embodiments described herein can encompass thosesituations in which any system is used to data from a subject. Further,those of skill in the art will recognize that the present techniques areapplicable to many different hardware configurations, softwarearchitectures, organizations, or processes.

While the detailed drawings and specific examples given describeparticular embodiments, they serve the purpose of illustration only. Thesystems and methods shown and described are not limited to the precisedetails and conditions provided herein. Rather, any number ofsubstitutions, modifications, changes, and/or omissions may be made inthe design, operating conditions, and arrangements of the embodimentsdescribed herein without departing from the spirit of the presenttechniques as expressed in the appended claims.

This written description uses examples to disclose the presenttechniques, including the best mode, and also to enable any personskilled in the art to practice the present techniques, including makingand using any devices or systems and performing any incorporatedmethods. The patentable scope of the present techniques is defined bythe claims, and may include other examples that occur to those skilledin the art. Such other examples are intended to be within the scope ofthe claims if they have structural elements that do not differ from theliteral language of the claims, or if they include equivalent structuralelements with insubstantial differences from the literal languages ofthe claims.

1-20. (canceled)
 21. A system for ECG electrode and leadwire connectionintegrity detection, comprising: a plurality of electrodes, wherein auniform spectral energy signal is to be injected into a subset ofelectrodes of the plurality of electrodes; and a computing devicecomprising a display, wherein the computing device is communicablycoupled to the plurality of electrodes and is configured to: acquireinput signals from an electrode; determine a frequency response from theelectrode based on the input signal from the electrode; and determineimpairments in the electrode and leadwire connection using the frequencyresponse over a range of frequencies.
 22. The system of claim 21,wherein the subset of electrodes is a right leg (RL) electrode.
 23. Thesystem of claim 21, wherein the subset of electrodes includes a rightarm electrode, a left arm electrode, a left leg electrode, a V1electrode, a V2 electrode, a V3 electrode, a V4 electrode, a V5electrode, and a V6 electrode.
 24. The system of claim 21, wherein thefrequency response is determined by calculating the Fast FourierTransform (FFT) of the input signal appearing at the electrode.
 25. Thesystem of claim 21, wherein the frequency response is used to determinean impedance of the electrode, and the impedance of the electrode isused to determine a connection impairment of the electrode.
 26. Thesystem of claim 21, wherein the uniform spectral energy signal is achirp signal.
 27. The system of claim 21, wherein the uniform spectralenergy signal is an impulse signal.
 28. The system of claim 21, whereinthe frequency response is used to detect and classify impairments in theelectrode and leadwire connection.
 29. The system of claim 21, whereinthe computing device is a patient monitoring system.
 30. Anelectrocardiograph (ECG) system, comprising: a plurality of electrodesincluding a right leg electrode and a second electrode, the right legelectrode to be driven by a chirp signal and to be releasably attachedto a patient, wherein an impedance between the second electrode and theright leg electrode is calculated over a range of frequencies and thecalculated impedance is used to determine a location of electrodeconnection impairment.
 31. The ECG system of claim 30, wherein the chirpsignal is a signal with a uniform spectral energy content.
 32. The ECGsystem of claim 30, wherein the plurality of electrodes form a 12-leadECG system.
 33. The ECG system of claim 30, wherein the second electrodeis any of a right arm electrode, a left arm electrode, a left legelectrode, or a chest electrode.
 34. The ECG system of claim 30, whereinthe calculated impedance is used to determine a location of a leadwireconnection impairment
 35. A method for electrocardiograph (ECG)electrode and leadwire connection integrity detection, comprising:injecting a chirp signal into a neutral electrode; measuring animpedance at a plurality of electrodes across a range of frequenciesfrom the chirp signal; calculating an impedance of pairs of electrodesof the plurality of electrodes from the measured impedance; anddetermining an impairment location based on the calculated impedance.36. The method of claim 35, wherein the neutral electrode is a right leg(RL) electrode of a 12-lead ECG system.
 37. The method of claim 35,wherein the calculated impedance is used to determine an electrodeimpairment location or a leadwire impairment location.
 38. The method ofclaim 35, comprising determining the impairment location prior toobtaining an electrocardiograph plot.
 39. The method of claim 35,wherein the calculated impedance is used to classify an impairment.